'No, no, no!' – What do top Japanese chefs make of Britain's high-street sushi?

Supermarket sushi sales are booming – even though a new study says Brits have no idea about the fish they are eating. So how authentic are our best-selling convenience brands? We asked two masters of the cuisine to give us their view

As the sticker rips on the third of our sushi lunch boxes, chef Yuya Kikuchi freezes, eyes fixed on a prawn nigiri. “Crazy,” he says, “no, no, no.” In all his 19 years making sushi, this prawn is one of the least appetising ingredients he has ever seen.

“This is too small, too thin. It’s crazy,” he says, raising the flacid crustacean to his eyes where it dangles limply.

We are taste-testing high-street sushi in Jugemu, his tiny wood-panelled restaurant in Soho, and so far it isn’t going too well.

Sushi sales in the UK have rocketed. High-street sushi chain Itsu’s sales have doubled in five years. Sainsbury’s says it sells 90,000 packs of sushi a week, with spikes during warmer seasons.

Yet despite the UK’s increasing love of raw fish, new research has found that some sushi bars and shops are are regularly mis-selling fish to unwitting British customers. A related survey found that the average British consumer was familiar with just two out of six common fish, with only about half recognising salmon and mackerel, and one in three identifying cod. The conclusion: we are eating more fish, but we often have no idea what it is.

After much coaxing, Kikuchi throws a small and tightly wrapped tuna maki into his mouth. “One,” he says between uncomfortable-looking swallows, “this is a one out of five. It is too dry. You see this rice? It is too pressed. High-street sushi absolutely cannot compete.

“Sushi looks simple: rice, fish, wasabi. But each ingredient is very important. The rice needs to be the correct temperature and texture, made with quality ingredients and skilled cooking. It’s very easy to tell if it is made by a professional or not,” he says.

In Kikuchi’s restaurant, which serves no more than 19 people a day, the rice is cooked to perfection. It is glossy, does not stick together and is served slightly warm. The fish is fresh, and bought in small quantities from one trusted supplier with availability dictating the menu. “Sushi is like a marriage. Not just rice and fish, but a new thing. This is sushi,” he says.

I deliver the same selection of sushi to Nobu’s head sushi chef Teruya Noriyoshi, who has worked for the high-end Japanese restaurant for 17 years in various glamorous locations around the world. He is now helping to set up its new venue in Shoreditch, east London.

“It’s important to make sushi by hand, not machine. Hands know about quality. Every time you touch the rice and fish, you can tell whether it’s good quality. You can’t learn to cook rice in a week or a month – it takes at least a year. It also depends on the seasons; you can’t follow one process every time,” he says.

So, do any of the selections from our high-street sushi banquet match up to these two chefs’ exacting standards?

Wasabi Rainbow Set, £8.49

Yuya Kikuchi: The tuna colour is not good ... it should be more red. And also it should be cut differently. They have cut it wrong. With the prawn nigiri, the rice is bigger than the prawn. This is not nigiri. Overall, it looks nice and colourful. But I don’t think it’s good quality. The taste isn’t bad, and the price and quality match, too. If you charged £30, then it wouldn’t be good. 2/5

Teruya Noriyoshi: The rice is good, without too much pressure because you can still feel the texture. The water ratio is not too bad either. The sesame seeds are too much and not roasted. The tuna is a little bit old – the colour shows it. And it has a frozen, ready-to-eat prawn. Still, this is more like sushi for me. It’s OK. If I had to eat one again it would probably be this. 3/5

Sainsbury’s On the Go. Photograph: Christian Sinibaldi for the Guardian

Sainsbury’s On the Go fish selection, £2.40

Kikuchi: The prawn is too thin and the rice is hard as stone. It doesn’t look good. I don’t want to try it. But if customers are happy, it’s OK. I like Sainsbury’s – I buy sardines from there. But it should try to make the sushi better. Their sushi is not for me. 1/5

Noriyoshi: It looks like toy sushi. The rice is dry. They have no choice because they have to keep it in the fridge, I understand that, so the problem with the rice is that it has too much water, so it has become tough. The rice isn’t high quality. Traditionally in Japan we don’t use smoked salmon, but it’s OK. In Nobu I also use it slightly smoked. 1/5

Marks and Spencer’s The Sushi Lover’s Collection. Photograph: Christian Sinibaldi for the Guardian

Marks and Spencer Sushi Lover’s Collection, £7

Kikuchi: The beetroot-cured salmon is very interesting. It’s a good idea. The sushi looks nice and the taste isn’t bad. The rice is hard, though. The fish is tuna maybe, but it’s not good. Maybe it’s chicken, I’m not sure. This prawn is the same as Sainsbury’s – this is the smallest size you can get from the suppliers. I wouldn’t eat it for lunch. 2/5

Noriyoshi: They use black sesame, poppy seeds and dill. That’s unique. But the rice is all stuck together – you can’t see any grains. I make a nigiri, and people try to use chopsticks because that’s traditional. But because the rice is soft, some people complain. Use your hands and dip only the fish in soy sauce, not the rice. 2/5

Taiko Ryori Sushi (sold in Waitrose), £5.50

Kikuchi: It’s a frozen prawn like the others. The salmon, avocado and crab stick is not bad but it’s not sushi. 2/5

Noriyoshi: The rice has no shape – you can’t see the grains. They have used powdered wasabi because it’s cheap – we also use this in Japan because real wasabi is expensive. I can’t say any more bad comments! 1.5/5

Itsu Best of Itsu, £7.99

Kikuchi: The bean and avocado isn’t bad. It’s the first time I’ve had this combination. The rice is much too sticky, if the rice was better it would be good. The tuna is hard, but the colour is good. I would never serve this in my restaurant, but it’s better than Wasabi. 3/5

Noriyoshi: The avocado and crab and the sashimi is not bad ... this part is a 3/5. It has a little bone in there. As much as we try to avoid it, sometimes a bone is hiding inside. With our salmon, we marinate it and cure it with salt for about an hour, then rinse it with vinegar. It tastes totally different. It gives it an umami flavour and takes out excess water from the fish, making it less fishy. They didn’t do anything to the fish. The sesame is too much and it’s not even roasted. The rice is too watery and has been pressed too much. Sushi has to have balance, with air inside. I would maybe eat this again. 2.5/5

Verdict

Kikuchi and Noiyoshi agree that it is almost impossible to compare high-street sushi with something that has been hand-made by chefs. It’s almost like two different cuisines. Refrigeration loses the smooth and melting sensation created by eating body-temperature rice. Cost control, and customer demand for out-of-season fish, means using frozen alternatives, which can affect texture and flavour.

Noriyoshi says: “Japanese people enjoy takeout sushi. If you compare with Japan, of course it is so much better there as people know the culture and customers are picky. Even sushi trains in Japan [conveyer-belt-style restaurants] have good sushi, because the fish quality is very good. They can afford to buy large quantities of high-quality fish. Even I eat it sometimes.”

Kikuchi is hopeful that the quality will go up once the UK market becomes more discerning. “High-street sushi in the UK isn’t bad – this is fine for the beginning,” he says. “If people start to eat it more, and learn more about sushi, they will understand what it should really be like.”